Engine starter drive



Dec. l, 1953 J. J. DIGBY ENGINE STARTER DRIVE Filed March 5, 1951 1 L ,MM d i Y M L 2 m@ M z DJ m m l m y a www@ u 5, /YL I- z .\z W Z 6- Lf 6 v N. 6l B 4M! /M QN 7 /5 c\v /JEM |M f M .4 9-. .o u 7 w .\7 l, pmi( a no? e, mm1 I. H l n w 8 Pw. a IIL .lll 4@ n 4 5 d MI5? 3 n j 9 I \ov 3 U Q 6 H \4 l/ 9 3 m 3 m 3 M m 8 6 5 .6 T 3 3 3 www 6 w Patented Dec. 1, 1953 ENGINE STARTER DRIVE `lames J. Digby, Elmira, N. Y., assigner to Bendix Elmira Heights, N. Y., a

Aviation Corporation corporation of Delaware Application March 5, 1951, Serial No. 213,943

(Cl. 'Z4- 7) 6 Claims.

The present invention relates to an engine starter drive and more particularly to starter gearing of the type in which energization of the starting motor causes engagement of the gearing, which engagement is maintained until the engine is reliably self-operative.

It is an object of the present invention to provide a novel starter drive of the above type in which the disengagement of the gearing is dependent upon the rotational speed of the starting motor.

It is another object to provide such a device in which the means for holding the gearing engaged is positive in character and is released at a predetermined rotational speed of the starting motor, substantially irrespective of the loads on the holding means.

It is another object to provide such a device which incorporates means for yieldingly transmitting torque back from the drive pinion to the starting motor when the engine starts, while permitting the pinion to overrun, in order to assist in accelerating the motor to the releasing speed.

It is another object to provide such a device in which the drive is small and compact as related to its torque-carrying capacity and is a selfcontained unit requiring no external stop for the pinion.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in idle position;

Fig. 2 is a similar view showing the parts in cranking position;

Fig. 3 is a view similar to Fig. 2 of a second embodiment of the invention.

In Fig. 1 of the drawing there is illustrated a power shaft I having a smooth reduced extension 2 providing a stop shoulder 3 against which thrust washers Il are seated. A screw shaft 5 is fixed on the end of the power shaft I by suitable means such as a cross pin 6, and a control nut 'I is threaded thereon and normally retained in its idle position by means of a spring detent 8 which seats in a depression 9 of the screw shaft when in idle position.

A pinion II is slidably journalled on the smooth i portion 2 of the power shaft for movement into and out of mesh with a gear I 2 of the engine to be started, the meshing position of the pinion being defined by its engagement with the thrust washers A.

Means for actuating the pinion from the control nut l is provided comprising a coupling member I3 splined to the pinion as indicated at it, and retained thereon by a lock ring I5 seated in the extended hub I6 of the pinion and normally bearing against an internal ange I'I in the coupling member. The pinion I l is yieldingly maintained in extended relation with respect to the coupling member I3 by means of a mesh-enforcing spring I8.

The nut l and the coupling member I3 are provided with coaxial cylindrical surfaces I9, 2| respectively, and a clutch spring 22 is mounted on said members in position to wrap down and couple the members together frictionally when the nut 'i is rotated by the power shaft in the direction to crank the engine as indicated by the arrow a. The cylindrical surfaces I9, 2| are enlarged slightly adjacent the ends of the clutch spring 22 as indicated at 23, 24, so as to provide an initial frictional engagement between the spring and the nut and coupling member, this frictional engagement being sufficient to transmit a predetermined small amount of torque back from the pinion to the power shaft when the pinion is caused to overrun the power shaft as the engine becomes self-operative. The clutch spring 22 is maintained under endwise compression between a flange 25 on the control nut 'I and a ange 26 on the coupling member I3 by means vof a barrel member 21, one end of which enters a groove 23 in the control nut as indicated at 29, and which has a ange 3l at its other end embracing the coupling member I3.

The screw shaft 5 is provided with an enlarged head 32, and a radial pin 33 is xedly mounted therein in any suitable manner and serves as a Divot for a movable abutment member 34 which accordingly swings tangentially to the drive. The surface of the head 32 of the screw shaft is provided with ratchet teeth 35 which cooperate with similar teeth 36 on the abutment member 34, the teeth being arranged to permit the latter to swing into operative position as shown in Fig. 2, but to positively prevent the same from returning to idle position while the teeth are engaged. The operating position of the abutment member is defined by a stop pin 3'! so located that when said member engages the pin the axis of the abutment member is nearly but not quite parallel to the axis of the drive. rThe angle between the axis of the abutment member and axis of the drive when in operative position is preferably in the neighborhood of 5 or 10 degrees.

Means for urging the abutment member toward its operating position and for yieldingly holding the ratchet teeth 35, 35 in engagement is provided in the form of a torsion and compression spring 38 anchored at one end of the pivot pin 33 and its other end to the abutment member as indicated at 39 (Fig. 2).

When the abutment member is in operating position as shown in Fig. 2, it provides a positive abutment which arrests demeshing movement of the control nut 'i at the position indicated by the traversing the pinion II into mesh with-the eri-,-

gine gear I2 until its movement is arrested by the thrust washers 4. If the-meshinglmovement is interrupted by abutment of the pinion teeth'- against the teeth of the engine gear, the spring' I8 is compressed until su'icienttorquefisbuilt up to index the pinion into proper registry with the tooth spaces of the engine gear, whereuponthe meshing movement is completed.

'When: theV longitudinal movement .of the :pinion is-arrested by the :thrust: washers, torque vis .transmitted from thexcontrol nut through-the clutch spring- 22 which wraps downand grips the surfaces I9, 2I so as to couple the nut. .1 tofthecoupling-member landpinion :II to crank .the engme. f Y

During the jmeshing'movement 'of the control nut, the abutment member ,f34'is permitted 'to rotate "under the impulse iofthe. spring- .38 until it 'occupies theposition shown iii-Fig. 2, where it isA positively -held by the engagement ofthe ratchet teeth VN35,' 365 Whenv the' engine res,acceleration of` the pinionbyfthe engine gear causes it to overrun 'the power shaft; and the Ynut 1 is threaded back along the screw'shaft 5`byfthe torque trans-l mittedcthrough `the clutchgspringiZZ by its-fric` tionalA engagement with-the :enlarged portions 23 24of the control-nut andcouplingfmember: This movement, howeverfis arrested .bythe abutment member 34-until`the l,engine has become reliably self-operative.; When". this occurs,- the starting motor .will have accelerated sufficiently :to cause centrifugal force'to move the 'abutment .member 34 radially outward 'against the compression of the spring Y33 so'as to disengage the ratchet teeth 35,` 36,".and-then to rotate the abutment member aga-instthetorsionalforceof the springrback to idle position,.whereupon the'control nut and its associated'parts are permitted .toreturnto'their idle-position where they are retained by the antidrift detent 8:!

Should the operator deenergize the starting motor before it has vattainedsuficient speedy-to ycause releaseof the abutment member 34,"if the engine remains self -operative, torque -is .transmitted'back from the pinion I I through the-.clutch spring 22 to gradually accelerate the power shaft and motor up tothe releasing speed, whereupon the pinion I I is demeshed in the usualmanner;

In' Fig. 3 of the drawing there is' illustrated `a second embodiment of "the invention Vwhichxis self-contained, in that no. external stop forthe pinion is required. As there shownythethreads of the screw shaft A terminate adjacent the free end ofthe screw shaft, forming abutments 42 'which arrest lthe -meshingv movement of the control nut 1 thereon. The anchoredfend ofthe screw shaft .5A-has a smooth reduced portion 43 on which a ring 44is Xedly mounted in'any suitable manner-,and performs the function'of the driving head 32 1in the yfirst embodiment 'of the invention.

The remaining parts of this embodiment are the same as in the first embodiment and are similarly numbered, and the operation of the drive is the same except that the meshing position of the pinion is `in this case dened by the abutments 42Aonthe screw shaft 'instead of. bythe thrust washers 4.

Although but two embodiments of the invention have been shown and described in detail, it will'be understood that other embodiments are possible and that changes may be made in the precise form and arrangement of the parts without departing from the spirit of the invention.

Iclaimc:

1. In an engine starter drive a power shaft, a screw'` shaft lxedthereon, a control nut threaded onthescrew shaft, a pinion slidably journalled onfthefpower shaft for movement into and` out of mes-h witha gear of the engine to be started; means connecting the control nut to the pinion including an overrunning clutch, a radial pin fixed to the screw shaft, an abutment member pivoted ,thereon :for-.movement intowand outqof position Afor 'blocking.-the demeshing movement. `(Jfiitlne. pinion; and centrifugallyreleasable means fort holding the-abutment memberin blocking position. z v Y 1 Y 2. An engine starter drive as set forth in :claim 1 -in which: the1 overrunning clutch incorporates a .lfrictioncoupling yieldably transmitting torque from.-=thef-pinionfto the :control nut when the pinion over-runs the power shaft Y 3. An engine starter drive as set forth in claim 1 rin which the .v-means `forf-holdingfthe abutment member in-blocking position comprises airatchet connection between: the-abutment member and the-screw shaft', and including'further a spring ony the pivot .pine urgingfthe abutment .member into blocking position, and the ratchetconnectiorrinto engagement..

.4.- An engine starter ,driveas `set -forth in claim l including; further Y' means Vfor arrestingj the swinging movement ofrv the yabutment member into blocking position before the abutment memberl becomes aimed-with the axis of :the power shaft.

5.In `an engine starter drive-a power shaft, a pinionrslidably journalled thereon for movement into-and outof meshwith-anengine gear, means responsivetol acceleration of the power Vshaft yfor moving the pinion into meshing position, .an abutment member,A mea-ns for pivotallymounting the abutment member on the power shaft for move-- ment into--andout of position forblocking-the demeshing movement of the pinion; yielding means-for movingythe--abutmentmembery into blocking position, and means for positively holding the abutment member in blocking position; said-i abutment member -beingmovable by centrifugal force to release the holding means and return the abutment `member to idle position rat a predetermined rotational speed of the powershaft.I Y

6; I AnV anti-kickout engine starter drive including-a pinion,means for moving the pinion Vinto and out of mesh with an engine gear andfor rotating the pinion; means including an'abutment member pivotally mountedon the. moving means, yielding means urging the abutment member into operative position for blocking demeshing movement of: the pinion, and,centrifugally-released means for positively holding the abutment member inoperative position.'-

JAMES J. DIGrBY.l

References CitedfzinV the file of this patent UNlTED STATES PATENTS Y Y Number Name DateA 1,906,067 Howard Apr..25, 1933 1,955,110 Brockwayv Apr. 1'7, 1934 2,004,643 I'. Whitney June 11, 1935 2,167,618 1 Lingo July 25, 1939 2,311,894:` Buxton 1 Feb. 23,1943 

